Molecular characterizations of microbial communities fouling painted and unpainted concrete structures

This study reports the use of culture-independent and culture-dependent approaches to identify naturally occurring communities of Bacteria and Fungi fouling the surfaces of concrete structures with and without an acrylic paint coating in Georgia, USA. Genomic DNA was extracted from four different sites and PCR amplification of bacterial ribosomal RNA (16S rRNA) genes and the internal transcribed spacer (ITS) region of fungal rRNA genes was conducted. Bacterial and fungal community composition was determined by restriction analysis of amplified DNA of eight clone libraries and sequencing. Five bacterial phyla were observed, and representatives of the phylum Cyanobacteria and the classes Betaproteobacteria and Gammaproteobacteria dominated the bacterial clone libraries. The ITS region of rRNA gene sequences revealed the dominant phylotypes in the fungal clone libraries to be most closely related to Alternaria, Cladosporium, Epicoccum and Udeniomyces. The majority of these fungal genera could be cultured from the sites and successfully used to foul concrete in laboratory-based experiments. While the fungal sequences were most closely related to cultured isolates, the vast majority of bacterial sequences in the libraries were related to uncultured environmental clones. Results show phylogenetically distinct microbial populations occurring at the four sites.